X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao106.cox.net ([68.230.241.40] verified) by logan.com (CommuniGate Pro SMTP 5.2.3) with ESMTP id 2959198 for flyrotary@lancaironline.net; Sun, 08 Jun 2008 22:51:33 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.40; envelope-from=rv-4mike@cox.net Received: from fed1rmimpo01.cox.net ([70.169.32.71]) by fed1rmmtao106.cox.net (InterMail vM.7.08.02.01 201-2186-121-102-20070209) with ESMTP id <20080609025047.UGWN1607.fed1rmmtao106.cox.net@fed1rmimpo01.cox.net> for ; Sun, 8 Jun 2008 22:50:47 -0400 Received: from wills ([68.105.85.56]) by fed1rmimpo01.cox.net with bizsmtp id beqs1Z0081CvZmk03eqtiE; Sun, 08 Jun 2008 22:50:54 -0400 Message-ID: <007201c8c9db$a2f07eb0$38556944@wills> From: "Mike Wills" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Mistral Crash Analysis Date: Sun, 8 Jun 2008 19:50:54 -0700 MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=response Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3138 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3198 Has anyone ever tried using a Supertrap on the rotary? Was talking with a guy this last weekend at the local EAA chapter meeting. Said he used to race an RX-7 and swore that the Supertrap quietted the beast and held up under the pressure. I'm skeptical but have had good luck with Supertraps on motorcycles and various hot rods. Maybe a custom built "super Supertrap" with 321 stainless or even Inconel discs? Might be worth a try. One thing is certain. My "muffler" isnt (a muffler that is). I need something better. Mike Wills RV-4 N144MW ----- Original Message ----- From: "Ed Anderson" To: "Rotary motors in aircraft" Sent: Saturday, June 07, 2008 2:48 PM Subject: [FlyRotary] Re: Mistral Crash Analysis > > Hey, Al, if it were not for rationalization mode, none of us would be > flying "auto" engines {:>). > > So, Al, why don't you post a sketch/drawing of your muffler design and > give us some details - dimensions/materials etc. You design may be the > answer someone has been looking for. > > Sounds like a good muffler design - I have two headers and two mufflers so > should one plug up, I have one to come home on. > > When I was expermenting with mufflers, I tried a number of approaches > with less than stirling success. One of the problems is the very powerful > shock wave of the exhaust pulse which I have had fatigue SS metal in a > matter of a few minues. > > The rotary is also pretty sensitive to back-pressure, so what kills the > noise generally does the same to the power. There was one design I tired > that used 3" dia SS disc in a tube with "Paddles" bent on the outer > permimeter. The ideal was that the shock wave would see solid metal and > be reflected - but the exhaust gas would cruve and flow around the paddle > blades. > > It worked (while it worked) , I flew from NC to Florida and it measurably > reduce the exhaust note (by something like 8 db), the problem was the > discs and the jam nuts I had holding them on a 3/8" dia SS rod (I don't > weld) I had through their center. At some point, some of them (I had 5 > discs in each tube) worked loose under the pounding . They then began to > act like a windmilling propeller (yes, they were spinning at high speed). > The effect was to expotentially increase the drag on the exhaust gas and > imped gas flow. > > I was later told by an observer that my rotary sounded just like a turbine > when I took off - (Yeah, Yeah I thought at the time - the poor mans > turbine.) But, later examination showed the dics had indeed been spinning > and had burnished the inside of the tube where they spun. Tracy was kind > enough to use his arc welder to weld the discs to the rods (that lasted > for about two weeks). > > While the disc were stationary they did reduce the exhaust noise by 8 db > and did not have any measureable effect on power - however, when they > started windmilling - the max rpm I could get out of the engine was 6000 > rpm. Fortunately more than enough - but far below my normal max of 6800 > rpm. > > By that the sixth experiment on mufflers, I sort of lost interest. So > went and got two HushpowerII mufflers and stuck them underneath. So far > they have survived the pounding of the turbo block without any ill effects > (about 50 hours on them). > > Good words to heed, as usual, Al. > > Ed > > > >> C'mon guys. You do this every time there's a crash. Instantly go into >> rationalization mode. It's unhealthy. Greatly increases risk builders >> won't take action. Increases risk you won't research it thoroughly. >> >> A healthy response would be:" Here's another example of how our engines >> produce unusually destructive exhaust temperature and pulses. We have a >> rich history of broken exhaust components. We need to be very thorough >> when designing and building exhaust." >> >> I designed my own muffler. It had two inlets, two outlets. So if (when) >> my muffler failed, it could never block both pipes. I also put loose >> safety wire around my pipes, because on a pusher loosing pipe wipes out >> prop. So basically, I assume stuff will fail, then design it to control >> the way it fails. I've heard of rotary guys doing same type of thing. >> This is a good time to share those key items. >> >> On your car, they deliberately design products to fail a certain way. >> They will make a component weak, so it fails first. They do that with >> wheels and hubs. So when the muffler fails, little pieces come apart, not >> big sections? >> >> You guys do a great job of sharing successes, design and construction >> details. This is another opportunity. >> >> -al wick >> >> >> >> >> > predisposed to bad mouth the rotary - this will only be more ammunition. >> "See! even with umpteen million dollars you can't get one to fly" {:>). >> But, I serious doubt it will effect many who have researched the rotary >> and come to understand its benefits - as for the rest, who cares {:>) >>> >> >> I'm certain it was a relief to Mistral that the culprit was not one of >> their engine components. >> >> >> >> Whew! a close one for sure. >> >> >> >> Hi Ed, >> >> >> >> Unfortunately, I bet the majority of people will only hear "Mistral >> rotary", "lost power", and "crash" :-( >> >> >> >> Rusty (RV-3 taking forever.) >> >> ____________________________________________________________ >> Orlando Vacations - Click Here! >> http://thirdpartyoffers.juno.com/TGL2141/fc/Ioyw6i3nK7u59LkagfZ5IcEgGqYcvPRCwA85GgQITbFK9vE7wPGKFP/ >> >> -- >> Homepage: http://www.flyrotary.com/ >> Archive and UnSub: >> http://mail.lancaironline.net:81/lists/flyrotary/List.html > > > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: > http://mail.lancaironline.net:81/lists/flyrotary/List.html >